Ring contractions of dihydro‐ and tetrahydro‐1,5‐benzodiazepines in electron ionization mass spectrometry

Abstract

Abstract Electron ionization mass spectra of a series of 2,4‐disubstituted dihydro‐ and tetrahydro‐1,5‐benzodiazepines are discussed. The fragmentation of these compounds is dominated by ring contractions of diazepine, which give both five‐ and six‐membered rings, benzimidazoles and quinoxalines. Tetrahydro compounds showed a tendency to eliminate one nitrogen from the ring system and give quinoline rings through NH 2 and NH 4 eliminations. The electron ionization spectra of cis and trans isomers of tetrahydro compounds are identical.